This crochet pattern is written for five sizes, toddler-adult. However, the designer mentions that you can use a smaller hook and thinner yarn to decrease the size further and make crochet baby mittens. The yarn is a very thick #6 super bulky yarn so dropping down to a bulky or even worsted weight yarn would make smaller mittens that are still warm enough for winter.

Snowy Mittens by KajaOfSweden